This invention relates to 2,6-disubstituted derivatives of chloronitropyrazines of the formula: ##STR1## in which A is defined as an amino substituent wherein at least one of the hydrogens of the amino substituent is replaced by a lower alkyl, an hydroxy substituted lower alkyl, an alkoxy substituted lower alkyl radical. It also relates to the process of preparing such compounds starting with the corresponding 2-halo-5,6-dichloro-3-nitropyrazine by reaction with a selected alkyl amine or substituted alkylamine to replace the 2-halo and 6-chloro substituents. This invention further relates to pharmaceutical composition of such compounds and to methods of treatment comprising administering such compounds to patients undergoing radiation treatment to enhance the effectiveness of such treatment. Thus, such compounds and compositions thereof are used to preferentially sensitize tumor cells to therapeutic radiation and thus increase the effective therapeutic ratio of radiation therapy.
At the present time, certain other unrelated compounds are in experimental clinical use as radiation sensitizers. However, these compounds--for example, metronidazole and misonidazole--suffer from the drawback that they also cause neurotoxicity which limits their usefulness. The compounds of the present invention are effective radiation sensitizers, but are believed to have a more favorable therapeutic ratio.